The present invention relates to treatment fluids that comprise protected scale inhibitors, and methods relating thereto.
Subterranean formations can often include complex mixtures of aliphatic hydrocarbons, aromatics, hetero-atomic molecules, anionic and cationic salts, acids, sands, silts, clays, and a vast array of other components. The conditions at which these components resided and experience during exploration and recovery operations are contributory factors to scale formation in the corresponding wellbores and related tools. As used herein, the term “scale” refers to a mineral or solid salt deposit that forms when the saturation of formation water to one or more minerals is affected by changing physical conditions (such as temperature, pressure, or composition), which causes minerals and salts previously in solution to precipitate into solids.
Scale deposits can form on any surface in a wellbore operation, including subterranean formations, production tubing, gravel packing screens, and other wellbore equipment. Scale can develop almost immediately, or build up over several months before becoming noticeable. The formation of scale can decrease permeability of the subterranean formation, reduce well productivity and shorten the lifetime of production equipment, and in extreme instances restrict or even completely choke production. In order to reduce or remove scale build-up, it is generally necessary to stop production, which is both time-consuming and costly.
The formation of scale is often controlled by the use of scale inhibitors. Scale inhibitors are typical compound, molecules, or polymers that have several moieties that chelate the minerals or salts that form scale, thereby inhibiting scale formation.
Oftentimes, an area of a subterranean formation where scale inhibition is desired is also an area where it is desirable to place particulates (e.g., in fracturing operations or gravel packing operations where particulate packs are formed). Further, in wellbore operations that place particulates, other additives like viscosifiers or resin systems are utilized. Viscosifiers typically provide for better suspensions and higher carrying capacity of the particulates in a treatment fluid, which, in turn, can yield more efficient and effective wellbore operations. Resin systems typically are used in conjunction with coatings on the particulates that can consolidate the particulates, make the particulates tacky, allow for formation fines to adhere to the particulates, and combinations thereof. Consolidated particulate packs can mitigate production the particulates and formation fines, which, in turn, enhances production efficiency.
However, some viscosifiers utilize metal crosslinkers and some resin systems utilize amine-based resin curing agents. These two additives can interact with chelating moieties of the scale inhibitor, which reduces the efficacy of the metal crosslinkers, amine-based resin curing agents, and scale inhibitors. To mitigate this deleterious interaction, the wellbore operations may have several injections of additives, which increases time and cost. Further, delayed-release solid particles have been developed to, in effect, release the scale inhibitor after the primary function of the metal crosslinkers and amine-based resin curing agents have been achieved. These delayed-release solid particles can, however, be expensive to manufacture. Therefore, a need exists for alternative technologies that allow for delaying the activity of scale inhibitors.